There is a trend in the power generation industry to move away from relatively high cost mechanical watt-hour meters towards lower cost more easily integrated solid state remote metering. Although integrated circuits have been developed for calculation of circuit parameters relevant to power metering, there remains a need for low cost solid-state energy measurement sensors that have increased immunity to electrical transients caused by the power supply network and the ability to accurately measure power consumption over a wide range of load and environmental conditions. There is thus a need for sensors that are galvanically isolated from the power supply network.
Additionally, power meters generally use discrete transducers with analog outputs to provide voltage and current information to the microprocessor circuitry that is used to computer power consumption. Due to the nature of the power measurement and constraints imposed by the required minimum size of power conductors, it is difficult to integrate the transducers into the same integrated circuit package as the microprocessor used for power computation. A transducer that provides a digital representation of the power parameters, such as the voltage and current of the load and provides this digital data on a galvanically isolated communication channel for easy integration with other metering functions would, therefore reduce cost and increase the reliability of solid-state utility meters.
A final consideration for power transducers is measurement resolution. For current measurement, there is an important trend to replace commonly used current transformers or Rogowski coils with Hall Effect Sensors or magnetoresistive sensors including anisotropic magnetoresistance (AMR) and giant magnetoresistance (GMR). Hall Effect devices are relatively expensive and lacking in absolute resolution. AMR and GMR devices although they are relatively high resolution devices, suffer from low signal amplitude and require careful attention to be paid to front end electronics design, which increases system complexity and size of the integrated circuit design and therefore increases cost. Tunneling magnetoresistance (TMR) devices, also called magnetic tunnel junction (MTJ) devices offers high resolution and large amplitude that can be used simplify front-end electronics design, thereby lowering total system cost.